6.3.3 Intermittent Lockups
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6. Lift the circuit breaker access door and visually confirm the setting as shown in
FIGURE 6-4.
Circuit breaker
7. If the setting is incorrect, use a small straight blade screwdriver to rest it accord-
ing to TABLE 6-1.
8. Close the circuit breaker access door.
9. Replace the power wiring access panel using all perimeter screws.
6.7 Power Line
Fuse Replacement
The Model 648 uses a low-power, start-up power supply to provide power to the main
contactor coil through multiple thermal safety switches. The start-up supply is
energized any time the three-phase power input voltage is connected to the
Model 648. This section deals with the fuses for this supply. If the power line fuses for
this supply are open, the Model 648 internal three-phase contactor will not close and
normal operation will not be possible. Access to these fuses is through the power
wiring access panel.
To avoid potentially lethal shocks, turn off the power supply and disconnect it from AC
power before performing this procedure.
For continued protection against fire hazard, replace only with the same fuse type and
rating specified for the line voltage selected.
Use this procedure to change the power line fuses.
1. Identify the power wiring access panel on the rear of the Model 648.
2. Turn the front panel line power switch off.
3. Remove mains power from the Model 648 fusing the disconnect switch.
4. Remove the perimeter screws holding the power wiring access panel.
5. Locate the two fuse holder assemblies as shown in FIGURE 6-2 and
in FIGURE 6-5.
6. Pull open the access door to remove a fuse.
7. Check the fuse for continuity. Replace fuse(s) if necessary. Fuses should be
replaced in pairs. Fuses are inserted small-end first as shown (FIGURE 6-5).
8. Close the fuse access door(s).
9. Replace the wiring access panel using all perimeter screws.
FIGURE 6-4
